This application claims priority of the following European applications:
Serial No. 00610012.7 filed Jan. 28, 2000
Serial No. 00610013.5 filed Jan. 28, 2000
Serial No. 00610014.3 filed Jan. 28, 2000
Serial No. 00610015.0 filed Jan. 28, 2000
The present invention relates to the field of medical devices and more particularly to vascular devices such as catheters and delivery systems for implantable devices.
Catheters for medical diagnostic or therapeutic use are well known. A catheter has a distal end and a proximal end, with a body extending therebetween and a lumen extending therethrough from end to end. A wide variety of catheters exists for percutaneous insertion by the Seldinger technique into the vascular system to accomplish diagnostic or therapeutic objectives. The vessels of the peripheral vasculature have a relatively large diameter and low tortuosity, the coronary vasculature is somewhat smaller and more tortuous, and the vasculature in the soft tissue of the brain and liver is of small lumen and is very tortuous.
In order to be able to access the various parts of the vasculature, the catheter needs to be flexible and to maintain its column strength when it follows a tortuous path. The contradictory requirements for flexibility and column strength are particularly pronounced in catheters for intracranial catheterizations used in a variety of diagnostic and interventional neurological techniques including delivery of contrast fluids, drugs or a vasoocclusive agent, treatment of tumors, aneurysms, AVS (arteriovenous shunts) and so forth.
When a central member is to be moved within a catheter or sheath to perform an activity at or beyond the distal end of the catheter, after the catheter has been positioned, the central member is to be pushed through the catheter lumen. The more tortuous the path and the smaller the catheter the more difficult it is to advance the central member through the catheter lumen. This difficulty is in particular pronounced in coaxial systems for intracranial use. Where the central member is a delivery device for an embolization coil and must be rotated to disconnect from the coil upon release at the treatment site, the central member must be capable of transmitting torque to its distal end for assured coil disconnection; one such prior art coil delivery system is disclosed in U.S. Pat. No. 5,122,136; but it is a common problem that such prior art coil delivery members have relatively high rigidity which is problematic in small or tortuous vessels with aneurysms. Where the device is a pusher to push a device such as a stent from the distal end of the catheter, the pusher must have substantial column strength as well as great flexibility.
Where a catheter is to be used for delivery of an endovascular prosthesis to a treatment site, such as a stent, a stent graft, a valve member, or a filter, where the prosthesis is compressed to pass through the catheter and then selfexpand upon release therefrom within a body lumen, the prosthesis must be constrained while within the catheter and imposes significant forces against the surrounding catheter body.
It is an objective of the present invention to provide a medical device that includes a distal area that is very flexible and yet easily pushable and capable of transferring torque in an assured, controllable manner.
It is another objective to provide a catheter system that makes it easier to advance the central member through the catheter also in cases where the catheter exhibits sharp turns.
It is further an objective to provide a catheter that resists the substantial radially outward forces of a compressed endovascular prosthesis contained within the distal end thereof, and yet be very flexible and capable of transferring torque.
It is yet another objective to provide a central member for movement within a catheter lumen that is very flexible, has substantial column strength and/or is capable of transferring torque.
The foregoing and other problems are solved and a technical advance is achieved in an illustrative medical device for passage along the vasculature of a patient, having a body portion comprising primarily a plurality of coils or turns of a plurality of wound filaments or wires. The medical device may be a catheter or may be one or more components of a delivery system for endovascular devices, such as a central member within a catheter, for example, a pusher or delivery device for an embolization coil. Two to twelve filaments such as wires, and preferably from four to eight wires, are preferably helically wound adjacent to each other as a group or row with a pitch corresponding generally to the aggregate width of the adjacent wires in the row.
The wound wires transfer torque and also force components directed in the axial direction of the medical device to the distal end thereof, and this construction is found to give a very high resistance to kinking of the medical device. When a catheter according to the present invention is heavily bent, the cross-section of the catheter maintains a circular shape. This provides a distinct advantage over prior art catheters which are deformed into an oval shape in cross-section when bent leading to kinking. The catheter surprisingly maintains its capabilities for transferring torque and push when it follows a tortuous path involving two or more loops, probably because of the excellent kinking resistance. These qualities facilitate placement of the catheter at the desired position in the vascular system, and by making the catheter system so that the inner surface of the catheter is mainly undeformable by a central member moving axially therewithin, it is virtually impossible for the central member to get stuck in the catheter wall, even in situations where the catheter is heavily curved. This is in contrast to prior art coaxial systems where the catheter is made of a soft material such as a resin, the inner surface of which is readily deformable in a local area, causing the formation of a small bead in front of the tip of the central member bearing against the wall of the curved catheter. It is an advantage of the catheter according to the present invention that the wall is primarily made of wires that provide a hard and relatively slippery inner surface resulting in low resistance to advancing the central member through the lumen of the catheter.
The inventive catheter maintains three valuable characteristics of very high flexibility, pushability and torqueability even when set in a very tortuous pattern involving two or more tight loops, and the catheter can thus be of use in very small and distant vessels such as deep brain sites accessed by intracranial catheterization. Preferably, a thin sealing coating of elastic, low-friction material, or adhesive material may be provided over the outwardly directed surfaces of the coiled wires or along the inner surfaces that define a lumen, or at least in recesses between abutting wires or in interstices between nonabutting turns between the groups of wires, thus sealing the interstices between the wires so that the catheter wall is leakproof especially where the device is a catheter or sheath.
Further, wires may have the same diameter in the group and extend the entire length of the device, or the device may have portions with wires of different diameters, lessening toward the distal end and thereby decreasing gradually in outer diameter; the device may also have a noncoiled part in the proximal region such as a supplementary cannula or tubing.
In the present context, the term xe2x80x9ccatheterxe2x80x9d is to be understood in the sense that it can be an ordinary catheter, but also a sheath, which is a short catheter, and in the latter case the central member can be a catheter, e.g., a catheter according to the present invention. The sheath can have a check-flow valve or a fitting at the proximal end in order to stop bleeding out of the puncture site. In one aspect, the catheter may be utilized without a guidewire. When intended for use in a soft tissue region, it is preferred that the distal end of the catheter is provided with a buffer member, such as a soft obturator, that distributes the force from the catheter tip over a large area so that damage to the vascular wall is avoided. The term xe2x80x9ccentral memberxe2x80x9d can be a member that simply blocks the distal opening of the catheter during inflation of a balloon for percutaneous transluminal coronary angioplasty; it may also be an embolization means such as a sack containing several occlusion coils, or a stent for expansion on a balloon, a sensor body for measuring pressure or temperature or the composition of blood, a physical shunt member, a retrieval wire or a forceps used to retrieve another member from a vascular site; or it can be a central member of some other kind.
In another aspect, the number of wires may vary along the length of the catheter, such as reducing the number of wires in the row during the winding operation in the distal direction, enabling a larger pitch angle and increasing the flexibility of the catheter proximate to the distal end.
In a second embodiment, the medical device may be a delivery system for a prosthesis such as a stent, a stent graft, a valve member, or a filter, wherein the prosthesis is compressible to be placed within a receptacle at the distal end of the delivery catheter and is then radially expandable upon delivery to a treatment site after being urged from receptacle. The delivery system has a catheter shaft with a receptacle that may be simply a distal end portion of the catheter shaft, but the receptacle may also be a separate tubular member that extends from the distal end of the catheter shaft, or optionally partially within the distal end. The receptacle, whether integral with the catheter shaft or a separate member, is primarily defined by a group of wires wound about a lumen, thus having the same advantageous properties of high flexibility and kink resistance as the catheter shaft; optionally and preferably, when the receptacle is a separate member, the catheter shaft may also be of the inventive type hereinbefore set forth. The receptacle may have a larger lumen dimension than the lumen of the catheter shaft, such as by having a smaller wall thickness through use of smaller diameter wire or grinding away an innermost portion of the coiled wires of the distal tip when integral with the catheter shaft, since the wall thickness required for resisting the outward pressure from the radially compacted prosthesis is smaller than the wire thickness required to transmit axial thrust over a long shaft distance, such as 80 cm or more, enabling the outer diameter to remain the same as that of the catheter shaft portion.
In a third embodiment, a prosthesis receptacle is a separate member and is fixed to the helically wound multiple filament row of wires of the catheter shaft, in axial extension thereof. This allows the prosthesis receptacle to be designed and manufactured independently of the shaft portion. The mounting in direct extension of the wire or wires of the catheter shaft makes the prosthesis receptacle follow torsional actions on the shaft portion. Although the prosthesis receptacle can be designed in any manner capable of resisting the outward pressure applied to the inside of the receptacle by the compressed prosthesis, it is preferred that the prosthesis receptacle be a tubular segment of multiple filament construction, such as a braided wire construction providing the prosthesis receptacle with a high flexibility. More preferably, the receptacle is a construction of a second helically wound group or row of multiple wires; this makes it possible to obtain a very diminutive outer diameter as only a single layer of wires is required.
In yet another embodiment, the medical device may be a pusher for use in a delivery system of the type described above, where the pusher is primarily comprised of multiple wires that are helically coiled, resulting in a hollow construction with torqueability and pushability similar to the shaft portion of the delivery device and with slightly greater flexibility due to the smaller outer diameter of the row of wires.
In still another embodiment, the medical device may be used in an introducer for an embolization device, where the delivery member comprises primarily a plurality of wires to provide the advantageous torqueability of the present invention. The distal end of the delivery member thus is able to be rotated from rotation of the proximal end thereof, and thus being disconnectable through unscrewing from the embolization device, a technique that causes only negligible influence on the vasculature while enabling precise maintenance of the embolization device in its desired position during detachment even in very tortuous paths to treatment sites such as intracranial locations.